A new report from Sen. Claire McCaskill (D-Mo.) found that five opioid manufacturers paid nearly $9 million to 14 outside groups between 2012 to 2017, alleging that the advocacy groups often “amplified messages favorable to increased opioid use.”

The groups — many of which work on chronic pain and other opioid-related issues — lobbied to defeat prescriber limits on opioids and many criticized facets of 2016 guidelines that limited the prescribing of painkillers from the Centers for Disease Control and Prevention (CDC), according to the report.

Additionally, the report noted a “lack of transparency” around the donors who give to the advocacy groups. While the groups aren’t required to disclose their donors publicly, McCaskill said that should be changed.

“The financial relationships between these groups and opioid manufacturers should be clear to the general public,” McCaskill said. “We passed a law ensuring the public had information on payments to doctors by pharmaceutical companies, and I can’t imagine why the same shouldn’t be done in this space.”

This is the second report on opioids from McCaskill, the ranking member of the Homeland Security and Governmental Affairs Committee. The reports come at a time when deaths from opioid overdoses continue to rise.

Purdue Pharma said in a statement: “We have supported third-party organizations, including with annual dues and unrestricted grants, that are interested in helping patients receive appropriate care and share our commitment toward addressing the opioid crisis.”

The company views the 2016 CDC guidelines as “an important public health tool.”

Depomed said its contributions averaged $20,000 per year to nine groups and that it believes it acted responsibly when it marketed its drugs. It said the money covered items such as corporate advertising and conference booth fees.

Insys said in a statement that “We believe that our 2017 charitable contributions, which have become the subject of media attention, are patient-focused.”

Mylan pushed back on its inclusion in the report, saying it had a “minuscule role in the manufacturing and marketing of opioids” and made limited payments, amounting to $20,250 over three years, to one group.

Several organizations said the money didn’t influence their groups, according to news reports.

Bob Twillman, the executive director of the Academy of Integrative Pain Management, told The Associated Press that “we really don’t take direction from them about what we advocate for.” His group received nearly $1.3 million from four opioid manufacturers.

The U.S. Pain Foundation said $2.5 million it received from one company went toward a fund to help cancer patients pay for pain drugs, and also noted that the money did not alter the group’s values in any way, according to Reuters.